JP2017106116A - Method for producing object by solidifying powder using laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an object having a thin wall, a complicated shaped and/or a large volume, and having no structural flaw.SOLUTION: A normal process producing an object by solidifying powder (P) including: a step a) where a powder layer (P) is stretched onto a work zone (Z); a step b) where the layer is compressed; a step c) where the first zone (7) of the compressed layer is solidified using a laser; a step d) where at least one of the second zones (11, 12, 13) in the compressed layer is solidified under solidification conditions selected in such a manner that the second solidification zones (11, 12, 13) has strength lower than that of the first solidification zone (7), where the second zones (11, 12, 13) are abutted against the zone (7) solidified in the step c); a step e) where the steps a) to d) are repeated till an object (1) can be obtained; and a step where, after the step e), when the object (1) is completed, the second zones (11, 12) are removed from the first zone (7).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for producing an object by solidifying a powder using a laser.

  The term “powder” in this application means a powdery substance composed of one or more elements and a mixture of a plurality of powdery substances. In other words, “powder” means a powder or a powder mixture. Such powders can be metals or minerals such as ceramic powders.

  Producing an object with more or less complex shape from a powder (some areas of the powder are spread beforehand in a thin layer) by solidifying by melting due to the effect of thermal energy given by the laser It is known. Hereinafter, the term “sintering” means solidification by laser treatment.

  Each layer of powder is sintered only in the areas that are to form the wall of the finished object before being spread and compressed into a further layer of powder. The term wall means in this application part of a component of an object. This element may be solid, have various geometric shapes, or at least partially define a predetermined volume. An object having at least a thin wall by this method, i.e. a wall having a thickness of less than 1 mm, or an object having a ratio of the height or diameter of the object to the wall thickness greater than 5 or having a complex shape with an undercut region When it is going to manufacture, it is difficult to implement by the existing method.

  Such difficulties are related to the sintering of the powders, and such difficulties cause wrinkles in the manufactured object, especially some walls of the object. In fact, the use of a laser to provide the local and high speed energy required to solidify the area that will form the wall of the object causes a significant local temperature rise of hundreds of degrees Celsius. Such an increase in temperature can cause residual stresses and local deformation of the wall of the object, especially when these walls are thin.

  Furthermore, deformation is seen in the so-called undercut region, i.e. in the region where the wall of the object protrudes into the region of the non-solidified powder. In fact, when the laser beam acts on the powder, a temperature increase due to radiation of the powder in the area adjacent to the area to be sintered occurs. If the adjacent area is an area located below the previously sintered area, in other words, the powder below the sintered layer where the adjacent area of the area to be sintered constitutes the wall of the object This temperature increase is particularly significant when located in a layer. In such a lower layer, the powder is located under the area where the wall overhangs, ie in the undercut area. The powdered material has a thermal conductivity that is lower than the thermal conductivity of the same material that is solidified and therefore has a higher density. This is due to the presence of a gas, for example air or nitrogen, between the particles of the powder material. This difference in thermal conductivity allows the powder that extends to the upper layer above the previously sintered layer to solidify during sintering to form the wall being manufactured, but is not sintered. There is also a solidification of the powder located in the lower layer below the layer forming the wall. As a result, unscheduled solidified regions are formed, such as for example a fold or raised surface.

  Patent Document 1 discloses a method of manufacturing an object by solidifying powder. The first layer of powder is deposited. Next, the first region of the layer corresponding to one section of the component part of the completed object is solidified using a laser. The second region of at least one of the layers is also solidified. The second region is in contact with the solidified first region. The solidification conditions are such that the solidified second region has a lower mechanical strength than the solidified first region. The completed object comprises a central region located at the core of the object and a surface coating layer surrounding the central region. The central region is partially solidified, whereas the surface coating layer is completely solidified, providing a high hardness for machining the outer surface of the object. Since this object takes the form of a solid volume, it does not contain thin walls. Therefore, there is no difficulty in carrying out the known sintering method.

German Patent Application Publication No. 10042132 (A)

  The present invention aims to remedy the above-mentioned drawbacks by a method for producing an object with thin walls, complex shapes and / or large volumes and without structural wrinkles.

  For this purpose, the invention relates to a method for producing an object by solidifying a powder or powder mixture as claimed in claim 1.

  Thus, the solidified second region having a lower strength is generated around the region forming one section of the component part of the object. This solidified second region is strong enough to support the solidified first region, thus preventing any deformation when manufacturing the object. This second region has a thermal conductivity that is closer to the thermal conductivity of the first region than the thermal conductivity of the powder or powder mixture, even though it is mechanically more fragile than the first region. For this reason, the difference between these thermal conductivities is small enough not to cause structural wrinkles in the object.

  An advantageous but optional form of this method is defined in claims 2-15.

  The present invention will be better understood by reading the following description of two embodiments of a manufacturing method by solidifying a powder using a laser according to the present invention, which is given by way of example only and with reference to the accompanying drawings, It will be well understood and further benefits will be clearer.

FIGS. 1 and 2 are schematic side views of the steps of depositing the layer and solidifying the layer using a laser, respectively, according to a method according to the prior art, with a wrinkle shown on the wall of the finished object. FIG. FIGS. 1 and 2 are schematic side views of the steps of depositing the layer and solidifying the layer using a laser, respectively, according to a method according to the prior art, with a wrinkle shown on the wall of the finished object. FIG. 3 to 6 are schematic views of the steps of the production method according to the invention, ie the spreading of the layers, the sintering of the first layer of powder and the spreading of the second layer of powder, shown at the same scale. It is. 3 to 6 are schematic views of the steps of the production method according to the invention, ie the spreading of the layers, the sintering of the first layer of powder and the spreading of the second layer of powder, shown at the same scale. It is. 3 to 6 are schematic views of the steps of the production method according to the invention, ie the spreading of the layers, the sintering of the first layer of powder and the spreading of the second layer of powder, shown at the same scale. It is. 3 to 6 are schematic views of the steps of the production method according to the invention, ie the spreading of the layers, the sintering of the first layer of powder and the spreading of the second layer of powder, shown at the same scale. It is. 7 is a cross-sectional view along the plane VII-VII of FIG. 6 before the finishing step of the object manufactured as described above, shown at the same scale. FIG. 8 is an enlarged view of the circular region VIII of FIG. 2 showing wrinkles appearing in the undercut portion when the wall is manufactured by the method according to the prior art.

  FIG. 1 schematically shows the production of an object 1 from powder P or a powder mixture (metal or ceramic). The object 1 has, in the embodiment, a component 2 (also called a thin wall, i.e. a wall less than 1 mm thick). The object 1 has a relatively large volume compared to its cross section. This object is hollow and its internal volume represents almost its entire volume. FIG. 1 shows the overhanging or undercut regions 3 and 4 of the wall 2 of the object 1.

  A cylinder 5 mounted rotatably in the direction of the arrow F1 shown in FIGS. 1, 4 and 6 extends and / or compresses the powder P along the direction of the arrow F2, preferably in multiple paths.

  Alternatively, a further extension member can be envisaged, for example a scraper located downstream of the cylinder along the direction of arrow F2.

  Alternatively, in accordance with the technical teaching of EP 1641580 (A), the outer surface of the cylinder 5 is not smooth but grooved, allowing the powder P to be picked up, spread and compressed.

  Thereby, the first layer 6 of the powder P compressed on the work area Z is formed. In the first layer, the thickness generally varies from 1 μm to 100 μm, preferably from 15 μm to 40 μm. This work area Z is formed by a substrate that can be translated along the direction of the arrow F3. The substrate is lowered when the layer of powder P is formed so that the cylinder 5 can spread and compress the powder P.

  Several areas of this layer 6 of powder P are sintered. That is, it is solidified by the heat energy given by the laser 8. The solidified region 7 constitutes the wall 2 of the completed object 1.

  FIG. 2 shows a so-called laser treatment or sintering step for producing the object 1 in a manner known in the prior art. Due to the action of the laser 8 shown schematically in this extended and compressed layer 6, folds 9 and 10 appear in the object 1.

  The first type of scissors consists of a deformation of the thin wall 2. This deformation 9 results from the release of local stress due to the action of the laser 8 causing the predetermined region of the wall 2 to rise by several hundred degrees Celsius.

  Another type of scissors shown in FIG. 2 is indicated by a turn 10 that extends inside and outside the object 1. In the case of undercutting, that is, in the region where the wall 2 protrudes from the powder P that occupies a part of the volume of the object, the turn 10 appears. There is a difference in thermal conductivity between the layer of powder P that has already been processed or solidified to form a section 2 of the component part 2 of the object 1 and the powder P that is to be processed or not solidified. . The thermal conductivity of the unsolidified powder is lower than that of the sintered powder or solidified material due to the presence of gas such as air or nitrogen between the powder particles. In other words, the powdered material has higher heat resistance than the solidified material. Thus, the action of the laser 8 on the powder has an effect beyond the area to which the laser is directed, resulting in solidification of the powder P located just around the area targeted by the laser 8. As shown in FIG. 8, when the powder P is located in contact with the wall below the wall 2, as shown in FIGS. 2 and 8, it is located at the free end of the wall 2, for example, toward the inside and outside of the object. Yield bear 10 As shown in FIG. 8, a deformation 9 directed inward of the object appears on the wall surface 20 between the powder P and the wall 2. During processing with the laser 8, heat energy is transferred from the upper layer 60 of the powder P to the powder located below the wall 2 by the wall 2. A portion of this powder then solidifies randomly and uncontrolled, producing deformation 9. In other words, the inner surface 20 of the wall 2 is not regular. When the free end of the thin wall 2 is subjected to the action of the laser 8 in order to solidify the further layer 60 of powder P, a deformation that forms the turn-up 10 appears due to the thinness of the wall 2.

  In the presence of soot and / or deformations 9 and 10, the passage of the cylinder 5 for spreading a further layer of powder P on the previously sintered layer 6 may cause surface flatness in the layer of solidified powder. Interrupted by lack and presence of obstacles. This new layer is therefore less spread and / or compressed and may not be compressed at all. Furthermore, translation of the roll may be hindered or prevented. The turn 10 may further alter the surface of the cylinder 5. Furthermore, such wrinkles and / or deformations 9 and 10 form structural weaknesses in the finished object 1.

  The present invention uses the same powder P or powder mixture to spread the powder using the same spreading member 5 in order to produce an object 1 without wrinkles and / or deformation and having a thin wall and / or undercut, The powder is to be compressed and processed using a laser 8.

  For this purpose, as shown in FIG. 3, in a first step, the first layer 6 of powder P is spread, compressed and treated with a laser 8. As described above, in this layer 6, the first region 7 is solidified and, in cross section, the wall of the object 1 to be produced is produced by a continuous layer. That is, the first region is one section of the constituent part of the object.

  In the second step, at least one second region of the powder P that does not constitute the finished object 1 (ie, this second region is not part of the object) is solidified. In the example, two second regions (indicated by 11 and 12) are envisaged. The areas 11 and 12 are adjacent to each other with or without abutting, and when the areas 11 and 12 are not in contact with each other, there is a 1/10 millimeter gap between the areas 11 and 12 and the area 7. . The dimensions of these areas 11 and 12 are substantially larger than the dimensions of area 7. Regions 11 and 12 are formed in the powder P on both sides of region 7 in this example. In other words, the regions 11 and 12 are located on both sides of a section of the wall 2 to be manufactured. In this second step, the operating parameters of the laser 8 are different. The operating parameters are suitable for incomplete solidification of the powder P in the regions 11 and 12. In other words, in the second step, the powder P is solidified, but the solidified powder P produces regions 11 and 12 that are less dense and / or more porous than the region 7 where the wall 2 is formed. . Thus, regions 11 and 12 are structurally weaker than region 7 for forming the wall of the object. However, it is strong enough to form a support or reinforcement of the wall 2 produced in the implementation of the method by treatment with the laser 8 (or other treatment known as sintering). Although regions 11 and 12 are weaker than region 7, they are more stable than powder P that is not treated with laser 8.

  One solution for obtaining the regions 11 and 12 is that the thermal energy supplied to the powder P in the second regions 11 and 12 is greater than the energy supplied to the powder P to solidify the first region 7. Is also small.

  This difference in thermal energy can be obtained, for example, by using a small laser power and / or by using the same laser power but using a higher scanning speed. It is advantageous to use the laser 8 with lower power and higher scanning speed.

  In a further embodiment not shown, the thermal energy variation is obtained by other means known per se, for example by adjusting the trajectory of the laser beam.

  For example, in the case of the metal powder P, the difference in energy used when the region 7 and the regions 11 and 12 are sintered is 10% to 20% of the thermal energy of the laser beam necessary for sintering the region 7. .

  In one embodiment, not shown, two lasers are used and the two lasers are different from or identical to each other, but with different settings, so as to produce region 7 and regions 11 and 12 simultaneously. In other words, the sintering steps of regions 7, 11 and 12 are not performed sequentially but are performed simultaneously. This solution can save time for manufacturing the object.

  In any case, it is advantageous that the laser used has a fixed wavelength. In other words, a single wavelength is used to sinter the regions 7, 11 and 12 of the layer 6 of powder P.

  In one preferred embodiment, the powder or powder mixture forming the layer 6 is homogeneous throughout the layer, simplifying the performance of the method.

  In a further embodiment not shown, the powder or powder mixture constituting the region 7 and the regions 11 and 12 is not the same. In this case, the nature of the powder forming the regions 11 and 12 itself contributes to its structural vulnerability.

  4 to 6 show an embodiment comprising the further step of sintering the powder P in the region 13 that does not constitute the object 1 (a region separate from these regions 11 and 12). This region 13, when sintered, forms a wall that surrounds the other regions 11, 12 and 7. In practice, the sintering of region 13 is performed according to the various options described above with respect to regions 11 and 12.

  In other words, the sintered area corresponding to the object 1 is surrounded by a wall. This wall 13 is sintered under conditions that are arbitrarily different from those applied during the sintering of the regions 7, 11 and 12. In this case, the conditions are suitable to make the mechanical strength of the wall 13 intermediate between the strength of the wall 2 and the strength of the regions 11 and 12. Alternatively, the mechanical strength of the wall 13 is the same as the mechanical strength of the wall 2. In this way, the wall 13 is easy to break when finishing the object 1 while protecting and reinforcing the support produced by the regions 11 and 12. The wall 13 is particularly beneficial when manufacturing large objects.

  Therefore, this third region 13 forms a stop wall. For this purpose, the third region forms an object having a simple geometric shape, in particular a cylindrical shape optionally with a circular bottom, according to the shape of the object 1.

  4 to 7, the difference between the line filling the regions 11 and 12 located inside the wall 13 in the radial direction and the line filling the region located outside the wall is the region 11 and 12 processed by the laser 8. And the difference in powder state between the outside and not solidified.

  As shown in FIG. 4, the spread of a further layer of powder P on the previously sintered layer is not hindered by the presence of soot.

  As shown in FIG. 5, the wall is held firmly in place by regions 11, 12, and 13 that have a lower strength and absorb the heat released by the radiation in the first region relatively similarly. Therefore, solidification using the laser 8 does not cause wrinkling or deformation of the wall 2. As shown in FIG. 5, in the final pass of the laser 8, the powder P is sintered and the wall 2 is completed by closing the inner volume of the object 1.

  Thus, when viewing the object 1 in the cross section of FIG. 7, the object shows a series of concentric regions. The first area from the center is the low intensity area 12 occupying the internal volume of the object. Another thin area forms the wall 2 of the object 1. Similarly, another thin region 13 surrounds the object 1. A region 11 having a low intensity similar to the region 12 is located between the wall 2 and the wall 13.

  Once the object 1 is completed, it is only necessary to remove the relatively low intensity areas 11 and 12 and the wall 13 by techniques known per se, for example by micro-sanding (polishing), micro-bead injection, brushing or water jet. Good. Regions 11, 12 and 13 are naturally scraped off by micro-sander finishing or micro-bead blasting well before the treatment reaches or degrades the wall 2 of the object 1.

  Using this method, objects with thin walls and / or complex geometric shapes, in particular objects with a large number of internal volumes, are produced. This method can be easily applied to various types of powders regardless of the shape of the object, regardless of whether they are metal powders or ceramic powders.

  By compressing each layer of powder, sintered regions 7, 11, 12 and 13 having a controlled thermal conductivity and thus having sufficient strength to prevent manufacturing wrinkles are obtained.

  This method can be used in a variety of existing equipment for solidifying a powder by using a laser to process a thin layer of powder as long as the value of the thermal energy supplied by the laser can be set.

  By using two powders of different types, one for producing the reinforced regions 11, 12 and 13 and one for producing the object 1, the object is rare and / or costly This costly material can be saved when made with.

  Such a method is suitable for producing precision objects and / or objects having complex shapes.

Claims (19)

A method for producing an object by solidification of a powder, wherein the produced object has a thin wall with a thickness of less than 1 mm,
at least,
a) using a spreading member to spread at least one layer of powder or powder mixture of metal or mineral on a flat work area;
b) compressing the layer extended in step a) with a compression member;
c) solidifying the first region of the layer compressed in step b) with a laser, wherein the first region corresponds to a section of the thin wall;
d) the two second of the layers compressed in step b) under solidification conditions such that each of the two solidified second regions has a mechanically lower strength than the solidified first region. Solidifying the region, wherein the two second regions abut against the solidified first region and are positioned on either side of the solidified first region, and step d) Solidified in step, and
e) repeating the group of steps a) to d) until the object is completed, in each iteration of the group of steps a) to d), before the group of steps a) to d). On top of said layer obtained by repeating the above, a new layer of at least one powder or powder mixture is first spread by carrying out step a) and then compressed by carrying out step b) and of steps c) and d). Solidified by performing steps;
f) after step e), mechanically removing the solidified second region from the solidified first region;
Including steps consisting of:
Method. Step d) is performed after step c),
The method of claim 1. Step d) is performed simultaneously with step c) using a laser different from the laser used in step c),
The method of claim 1. In the layer extended in step a), the at least one powder or powder mixture is homogeneous throughout the layer,
The method of claim 1. The at least one powder or powder mixture includes a first powder or powder mixture and a second powder or powder mixture different from the first powder or powder mixture, and the first region is the first powder. Or formed from a powder mixture, wherein the two second regions are formed from the second powder or powder mixture,
The method of claim 1. Further comprising, after step c), during step g), solidifying the third region of the layer compressed in step b),
Step g) under solidification conditions such that the solidified third region has a mechanically smaller strength than the solidified first region and a mechanically greater strength than the two second regions. Solidified in
During step e), in each iteration of the group of steps a) to d), step g) is also repeated, and during step f) the solidified third region is mechanically removed. It is characterized by
The method of claim 1. During step g), the third region is solidified by using the laser used in step c), and using the thermal energy supplied by the laser, the first region in step c) Intermediate thermal energy that is smaller than the thermal energy supplied to solidify and larger than the thermal energy supplied to solidify the two second regions in step d) is supplied to the third region. It is characterized by being
The method of claim 6. Step g) is performed simultaneously with step c), using a laser different from the laser used in step c),
The method of claim 6. The third region includes the first powder or powder mixture in which the at least one powder or powder mixture is different from the first powder or powder mixture, and the first powder or powder mixture is different from the first powder or powder mixture. A region is formed from the first powder or powder mixture, and the two second regions and the third region are formed from the second powder or powder mixture,
The method of claim 6. During step f), the second region is removed from the first region by microsanding, microbead spraying, brushing or water jet,
The method of claim 1. During step d), the two second regions are solidified by using the laser used in step c),
The method of claim 1. During steps c) and d), a plurality of said lasers are used at a single wavelength to solidify said first region and two said second regions,
The method of claim 3. During step f), the third region is removed from the first region by microsanding, microbead spraying, brushing or water jet,
The method of claim 6. During step d), using the thermal energy supplied by the laser that is lower than the thermal energy supplied to solidify the first region in step c), low thermal energy is reduced to the two first It is supplied to two areas,
The method of claim 11. During steps c) and d), the laser is used at a single wavelength to solidify the first region and the two second regions,
The method of claim 11. In step d), the laser is used at a lower power than the power used by the laser in step c),
The method according to claim 14. In step d), the laser is used at a scanning speed higher than the scanning speed of the laser in step c).
The method according to claim 14. In each layer, the dimension of the two second regions is larger than the dimension of the first region.
The method of claim 1. In step e), the first region solidified by the implementation of step c) in a new layer of at least one powder or powder mixture for at least one iteration of the group of steps a) to d) covering one of the two second regions solidified by the implementation of step d) in the layer obtained by the previous iteration of the group of a) to d),
The method of claim 1.

Images